A traffic information management system such as a probe car system (also called a probing car data system) has been recently developed which allows vehicles traveling on open roads as a probing sensor to collect information on road traffic or traffic flow. This system includes a management center to collect probe information including a current position, a speed, and sampling time of each probe car via a communications means. The management center analyzes the collected probe information to thereby generate road traffic information on road states (e.g., congested, frozen, or snowed state) for providing to drivers.
Patent document 1 describes an example of the probe car system. A probe car has a terminal, which periodically records positional and temporal information on areas, where the probe car travels, and uploads the recorded information as probe information to a management center, at periodic intervals or at a predetermined time such as a time when a congested state is detected. The management center stores the probe information uploaded and detects a congested state based on the current probe information and previous probe information. The management center then generates congestion information to be provided by referring to the detected results and map data.                Patent document 1: JP-2002-251698 A (U.S. Pat. No. 6,546,330 B2)        
In such a probe car system, it is preferable that probe information is uploaded from each probe car to the center in a real-time basis. To that end, each probe car typically uploads the periodically recorded probe information at periodic intervals and at a specified time such as a time when a congested state is detected. As a result, the data volume uploaded from multiple probe cars inevitably becomes large, which results in significant increase in a load of the management center. For instance, data in the probe car system are uploaded using a mobile communications network operated by a wireless communications service company, so costs for uploading the data cannot be ignored. Thus, such a probe car system using the mobile communications network is not easily established as a business model.